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At least 883 records · Page 49Linked to original sources
PubMed1994

Interaction of anionic compounds with gelatin. II: Effect on some physicochemical properties of gelatin.

The interaction of gelatin with four monosulfonated or monocarboxylated azo dyes was investigated by measuring the surface tension and intrinsic viscosity of gelatin solutions containing the dyes at different concentrations, the rigidity and melting point of their gels, and the moisture regain of their films. The dyes, which were used as models for anionic drugs, differed in the size of their aromatic hydrocarbon moieties. Surface tension measurements showed that the gelatin did not affect the critical micelle concentration of the free dyes and that the bound dyes increased the surface activity of the gelatin. The dyes reduced the intrinsic viscosity of gelatin by as much as 2/3. They also lowered the rigidity and the melting point of dilute gelatin gels and reduced the moisture regain of dry gelatin films. These changes became more pronounced with increasing dye concentrations. The effectiveness of the dyes in producing these changes increased with the size of their hydrocarbon moieties because, as had been shown in a previous study, increasingly larger hydrocarbon moieties increased the binding of the dyes to gelatin. At the pH of the measurements, which was 1.9 units below the isoelectric point of the gelatin, the gelatin was a cationic polyelectrolyte. Binding of the dye anions by ion pairing, hydrogen bonds, and other secondary valence forces rendered the gelatin less ionic and less hydrophilic, which accounts for the present observations.

Anions↗
PubMed2005

Quartz crystal microbalance bioaffinity sensor for biotin based on mixed self-assembled monolayers and metastable molecular complex receptor.

A quartz crystal microbalance (QCM) sensor was proposed for the detection of small molecule biotin based on the mixed self-assembled monolayer (SAM) of thiols on gold substrate and the bioaffinity difference between an analyte (biotin) and an analogue compound (HABA) in binding avidin. Avidin formed a metastable complex with 2-[(4-hydroxyphenyl)azo]benzoic acid (HABA) immobilized on the crystal surface. When the sensor contacts a sample solution containing biotin, the avidin was released from the sensor surface to form a more stable complex with biotin in solution. The frequency change recorded is proportional to the desorbed mass of avidin, and there is a clear mathematic relationship between the frequency change and the biotin concentration. The use of mixed SAMs allows the stable attachment of bioreceptor molecules on the QCM, and enhances the amount of the immobilized molecules on the QCM, as a longer "space arm" in the mixed SAMs makes this monolayer membrane more accessible to capture the immobilized molecules. The proposed bioaffinity sensor has nice response to biotin in the range of 0.017-1.67 microg/mL. The sensor could be regenerated under very mild conditions simply by reimmersion of the sensor into a biotin solution to desorb the surplus avidin.

Azo Compounds↗